Multiple Sclerosis in Island Populations: Prevalence in the Bailiwicks of Guernsey Andj7ersey 23
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222Journal ofNeurology, Neurosurgery, and Psychiatry 1995;58:22-26 Multiple sclerosis in island populations: J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.58.1.22 on 1 January 1995. Downloaded from prevalence in the Bailiwicks of Guernsey and Jersey G Sharpe, S E Price, A Last, R J Thompson Abstract ous neurological disability in young adults; it The aim of this study was to establish for affects some 60 000 people in the United the first time the prevalence of multiple Kingdom and perhaps two million people sclerosis in the Bailiwicks of Guernsey worldwide.' The disease shows an unusual and Jersey, as representing the most geographical distribution in becoming com- southerly part of the British Isles. All moner with increasing distance from the patients with multiple sclerosis in the Equator in both the northern and southern Channel Islands resident on prevalence hemispheres.2 There is evidence for a similar day were identified by contacting all geographical gradient in the British Isles.2 medical practices, Multiple Sclerosis, Different studies have reported multiple scle- and Action Research for Multiple rosis to be 1 9 to 3 1 times commoner in Sclerosis societies by letter and visits. women than men and to have a peak age of The crude overall prevalence rates were onset of about 30 years, being rare in child- 1131100 000 (95% confidence interval hood and after the age of 50.2 The clinical fea- (95% CI) 90-3-135.7) and 86-7/100 000 tures, sex ratio, and age specific incidence (95% CI 63.3-110.0) for the Bailiwicks of curves for multiple sclerosis are similar what- Jersey and Guernsey respectively. When ever the underlying frequency of disease, sug- standardised to the age and sex structure gesting the same worldwide aetiology.2 of a previously reported Northern Ireland Among the many epidemiological surveys population the standardised prevalence of multiple sclerosis in the past 40 years, sev- ratios were 120-21100 000 (95% CI eral intriguing reports have studied the preva- 96-0-144-3) for Jersey and 95 61100 000 lence of the disease in geographically defined (95% CI 69-9-121.3) for the Bailiwick of island populations. The Orkney and Shetland Guernsey. When compared with recent islands have the highest prevalence of the dis- studies in the northern United Kingdom ease ever recorded-namely, 309 and 184 per the prevalence rates for multiple sclerosis 100 000 respectively.' The prevalence on in the Channel Islands lend some support Sardinia4 and Sicily5 has been reported to be to the proposed latitudinal gradient in the over 45 per 100 000, whereas on nearby British Isles although the standardised Malta the prevalence is tenfold lower.6 prevalence ratio in the Bailiwick ofJersey Clustering of cases of multiple sclerosis has is similar to those found in recent studies been recorded on Orkney7 and on the small http://jnnp.bmj.com/ of southern Britain. The standardised island of Key West off the coast of Florida.8 prevalence rates of probable and definite An "epidemic" of multiple sclerosis in the multiple sclerosis for the male popula- Faroes after occupation by British troops has tions were 37 31100 000 (95% CI 17-9-56.7) been proposed,9 and a similar rise in preva- for the Bailiwick of Guernsey and lence after troop incursions has been claimed 45 51100 000 (95% CI 26.3-64.7) for the on Orkney,'0 Iceland," and Sardinia.'2 That Bailiwick ofJersey whereas the standard- the incursions caused the apparent increase in on September 26, 2021 by guest. Protected copyright. ised prevalence rates for the female popu- the prevalence of multiple sclerosis in these lations were 97 51100 000 (95% CI situations has in most cases been disputed.2 73-9-143.5) and 139*5/100 000 (95% CI The Channel Islands lie 70-100 miles 112-6-181-2) respectively. Thus there is a south of the coast of England between 490 striking and unexplained 43% higher and 500 latitude and about 10-30 miles west prevalence of probable and definite mul- of the French coast, with the nearest island University Clinical tiple sclerosis in the female population of (Alderney) only eight miles from the Biochemistry, Level Jersey compared with that of the Cotentin peninsula. The British Channel D, South Laboratory Block, Southampton Bailiwick of Guernsey. This seems to be Islands are not part of the United Kingdom, General Hospital, due to an unusually low prevalence of the but are crown dependencies allied to the Tremona Road, disease among the female population of English crown since the Norman invasion. Southampton S09 4XY, UK the Bailiwick of Guernsey compared with They represent the most southerly part of the G Sharpe that of the United Kingdom mainland. British Isles. These Islands were invaded by S E Price Germany in June and July 1940 and liberated A Last (3 Neurol Neurosurg Psychiatry 1995;58:22-26) in May 194513 and were the only part of the R J Thompson British Isles occupied in the second world Correspondence to: Professor R J Thompson. war. The islands are divided into the Received 11 February Keywords: multiple sclerosis; prevalence survey Bailiwicks of Guernsey and Jersey. The 1994 and in revised form 3 May 1994. Bailiwick of Guernsey consists of Guernsey, Accepted 13 May 1994 Multiple sclerosis is a common cause of seri- Alderney, Sark, and other small islands, and Multiple sclerosis in island populations: prevalence in the Bailiwicks of Guernsey andJ7ersey 23 the Bailiwick of Jersey contains several small ple sclerosis was then subjected to careful J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.58.1.22 on 1 January 1995. Downloaded from uninhabited islands with only Jersey itself investigation. Sufficient clinical details to populated. Health care services in the two allow classification by both the criteria of Bailiwicks are independent of the NHS and of Poser et al 19 and of Allison and Millar'0 were each other. Also, as a popular holiday destina- sought. This was obtained either by three tion and an attractive residential choice due to authors (GS, SEP, AL) being allowed access favourable tax concessions, the Channel to the patients' notes or by the medical practi- Islands are not as geographically isolated as tioners filling in a detailed questionnaire. The some other islands-for example, Orkney and hospital notes of patients who had attended Shetland.7 No previous survey of the preva- the Wessex Neurological Centre were also lence of multiple sclerosis in the Channel studied. Local Multiple Sclerosis Societies Islands has been carried out. The present were requested to ask their members to supply study was undertaken to determine the preva- details of place of birth and age of onset of the lence of multiple sclerosis in the two disease. Forty eight patients on Jersey and 36 Bailiwicks in the light of recent estimates of on Guernsey and Alderney who volunteered the prevalence of multiple sclerosis in south- had a venous blood sample taken by a ern Britain,'4-18 and the proposed north-south member of the team. gradient in the prevalence ofmultiple sclerosis in the British Isles.' STATISTICAL ANALYSIS Population statistics were obtained from the census taken on prevalence day on Jersey,21 Methods Guernsey,22 and Alderney." No formal census CASE ASCERTAINMENT data are gathered on Sark and it was esti- A list of potential patients with multiple scle- mated that 560 people were resident there: we rosis was compiled with information obtained did not find a single case of multiple sclerosis from several sources, as the Southampton in this population and have excluded it from study'6 had shown the value of this approach. further analysis. To allow for differences The medical practitioners from both between islands in age and sex structure and Bailiwicks were a major source ofinformation. to allow comparison with published work, all We also received help from the Multiple crude prevalence data have been standardised Sclerosis and Action Research for Multiple against the 1961 Northern Ireland popula- Sclerosis (ARMS) Societies in both sets of tion24 by two different methods. The indirect islands, and also from the hyperbaric oxygen method was used to calculate standardised unit on Guernsey. The nearest British major prevalence ratios with 95% confidence inter- referral centre for neurology is the Wessex vals (95% CIs) for each Bailiwick. To test the Neurological Centre at Southampton; this has significance of differences in prevalence become the predominant specialist referral between the Islands and the 1961 Northern centre for the Channel Islands but many Ireland population for specific age groups, it patients have been seen elsewhere. Also, a was assumed that the observed number of consultant neurologist from Southampton cases follows a Poisson distribution with a visits Jersey regularly. Consultant neurologists mean equal to the expected number of cases at the Wessex Neurological Centre were under the standard prevalence rates. The http://jnnp.bmj.com/ therefore approached. direct method was used to calculate age stan- From these sources we compiled a provi- dardised prevalence rates for each Bailiwick sional list of potential cases of multiple sclero- and the difference in standardised rates sis covering the Bailiwicks of Guernsey and between islands, along with 95% CIs.25 Jersey. This was then used for a more detailed study. Medical practitioners were contacted again by letter and requested to provide Results details (name, date of birth, sex, and whether The provisional register of potential patients on September 26, 2021 by guest. Protected copyright. the patient was aware of the diagnosis) of any with multiple sclerosis in the Channel Islands patients under their care with multiple sclero- contained 193 names; of these 45 were even- sis who were alive and resident on the tually excluded because they were not resi- Channel Islands on prevalence day.